Oxidative dehydrogenation system

ABSTRACT

An improved oxidative dehydrogenation system recycles separated water from the system to a catalytic oxidation reactor at which location organic compounds in the separated water are converted to materials such as carbon dioxide, carbon monoxide and water vapor with the resultant treated water being recycled to a dehydrogenation catalytic reactor of the system.

In an oxidative dehydrogenation system utilized for oxygenating anddehydrogenating a hydrocarbon feed stream to form a resultant productfrom which water is separated, the separated water is generallysufficiently contaminated with hydrocarbons to cause said water to beundesirable for reuse in the process. This separated water hasheretofore been disposed of which disposal has represented a relativelylarge expenditure of time, labor, and equipment owing to its volume andundesirable characteristics.

This invention therefore resides in an oxidative dehydrogenation systemwherein separated water is recycled from the system to a catalyticoxygenation reactor at which location organic compounds in the separatedwater are converted to harmless materials such as carbon dioxide, watervapor and carbon monoxide with the resultant treated water beingrecycled to a dehydrogenation catalytic reactor of the system.

Other aspects, objects, and advantages of the present invention willbecome apparent from a study of the disclosure, the appended claims, andthe drawing.

The drawing is a diagrammatic view of the oxidative dehydrogenationsystem having the improvement of this invention.

Referring to the drawing, a steam drum 2 is connected to a furnace 4having an air stream 6 for mixing air and steam and heating said air andsteam mixture to a preselected temperature.

A dehydrogenation reactor 8 having catalyst 12 therein receives theheated air-steam mixture from the furnace 4 and a hydrocarbon feedstream 10. In the reactor, the hydrocarbon feed stream contacts thecatalyst 12 in the presence of air and steam and converts thehydrocarbons, for example from butene to butadiene. The effluent stream14 from the dehydrogenation reactor 8 passes through other processequipment, such as for example a quench tower 16, a separator 18, and agas processing apparatus 20 for further processing.

The effluent stream 14 discharging from the dehydrogenation reactorcomprises water, dehydrogenated hydrocarbon, oxygenated hydrocarbonderivatives, and unconverted hydrocarbon.

At a locus downstream of the reactor 8, water is separated from theproducts comprising the effluent stream 14 and recycled via conduit 22to the steam generator 59 and thence to steam drum 2.

In the process, excess water is received by the steam generator. Thisrecycle water is passed from the steam drum via conduit 24 into anoxidation reactor 26 which is connected via conduit 28 to the furnace 4for receiving the heated air-steam stream therefrom.

A catalyst 30 in the oxidation reactor 26 converts the organic compoundsin the separated water from the steam drum into carbonaceous gas, suchas carbon monoxide and/or carbon dioxide and into water vapor forexample.

The effluent from the oxidation reaction 26 which comprises the treatedwater, generally as steam, is passed via conduit 32 into thedehydrogenation reactor 8.

It is preferred that conduit 32 be associated with the hydrocarbon feedstream 10 at a location upstream of the reactor 8 for mixing thehydrocarbon feed stream with the treated water effluent from the reactor26 to form a resultant mixture for passing the resultant mixture intothe dehydrogenation reactor 8 via a single conduit 34.

By utilizing the method and apparatus of this invention, a basic problemin oxidative dehydrogenation processes is the elimination of by-productoxygenated organic material. To do this the by-product organics ofdiverse and small quantities are being removed by water and this leadsto the problem of the disposal of the contaminated water. This inventionprovides a process that eliminates all organics in the water and resultsin their conversion to carbon monoxide and carbon dioxide which can bedisposed of to the air. The process is a continuous one and operatesconcurrently with the plant facilities.

The following is an example calculated material balance more fullydescribing an example process of this invention.

                                      TABLE I                                     __________________________________________________________________________              Stream Number - Pounds per Stream Hour                              Component                                                                              10   36   38   28   6   34   14   42   44   46   48                  __________________________________________________________________________    Nitrogen           72,547                                                                             72,547                                                                             72.547                                                                            72,547                                                                             72,547                                                                             72,547                                                                             72,547                                                                             72,547                   Carbon Monoxide                       10,096                                                                             10,096                                                                             10,096                                                                             10,096                   Oxygen             22,627                                                                             22,627                                                                             22,627                                                                            22,027                                                                             7,095                                                                              7,095                                                                              7,095                                                                              7,095                    Methane                               46   46   46   46                       Ethylene                              134  134  134  134                      Ethane                                17   17   17   17                       Carbon Dioxide                        3,326                                                                              3,326                                                                              3,326                                                                              3,326                    Propylene                                                                              304                     304  967  967  967  967                      Propane  15                      15   78   78   78   78                       Isobutane                                                                              670                     670  670  670  670  670                      Isobutylene                                                                            45                      45   11   11   11   11                       Butene-1 10,695                  10,695                                                                             1,971                                                                              1,971                                                                              1,971                                                                              1,971                    Butadiene                                                                              879                     879  31,726                                                                             31,726                                                                             31,726                                                                             31,726                   n-Butane 590                     590  590  590  590  590                      Butene-2 trans                                                                         21,317                  21,317                                                                             7,071                                                                              7,071                                                                              7,071                                                                              7,071                    Butene-2 cis                                                                           16,382                  16,382                                                                             4,521                                                                              4,521                                                                              4,521                                                                              4,521                    Vinyl Acetylene                                                                        147                     147  145  145  145  145                      C.sub.5 +                                                                              17                      17   17   17   17   17                       Aldehyde and  602  583  583      23   768  768  752  38   714                  Acid                                                                         Water         433,024                                                                            433,024                                                                            419,603  466,203                                                                            479,624                                                                            479,624                                                                            469,626                                                                            6,710                                                                              462,916               Total  51,062                                                                             433,626                                                                            528,781                                                                            615,360                                                                            94,574                                                                            612,398                                                                            612,421                                                                            612,421                                                                            602,410                                                                            138,779                                                                            463,630             Temp., ° F.                                                                     150  310  318  1,152                                                                              350 1,050                                                                              1,125                                                                              410  245  130  130                 Pressure, psia                                                                         65   80   75   55   80  45   37   34   32   30   30                  __________________________________________________________________________    Component                                                                              50   52   54   56   60  58   60   62   22   61   32                  __________________________________________________________________________    Nitrogen                              72,547              72,547              Carbon Monoxide                       10,096              160                 Oxygen                                7,095               22,027              Methane                               46                                      Ethylene                              134                                     Ethane                                17                                      Carbon Dioxide                        3,326               1,000               Propylene                             967                                     Propane                               78                                      Isobutane                             670                                     Isobutylene                           11                                      Butene-1                              1,971                                   Butadiene                             31,726                                  n-Butane                              590                                     Butene-2 trans                        7,071                                   Butene-2 cis                          4,521                                   Vinyl Acetylene                       145                                     C.sub.5+                              17                                      Aldehyde and                                                                           707  637  86   54       7    38   19   600  200                       Acid                                                                         Water    458,316                                                                            412,484                                                                            55,830                                                                             46,600                                                                             45  4,600                                                                              6,710                                                                              13,421                                                                             334,000                                                                            334,000                                                                            466,203               Total  459,023                                                                            413,121                                                                            55,916                                                                             46,654                                                                             45  4,607                                                                              138,779                                                                            13,440                                                                             334,600                                                                            334,200                                                                            561,937             Temp., ° F.                                                                     130  240  210  310  310 130  130  300  130  250  1,450               Pressure, psia                                                                         50   100  100  80   80  50   30   65   80   75   55                  __________________________________________________________________________

Examples of catalyst 12 are as follows:

A typical catalyst in 12 comprises iron oxide, chromium oxide and analkali metal carbonate such as potassium carbonate. Another catalyst isstannic phosphate. In general the oxidative dehydrogenation process iswell known in the art. For example, see U.S. Pat. Nos. 3,320,329 and3,409,697.

Examples of catalyst 30 are as follows:

Catalysts that can be used in 30 are for example zinc aluminatepreferably promoted by a small amount of metal active for initiatingoxidative reactions. Such metals can be found in Groups IIIB, IVB, VB,VIB, VIIB, VIII, IB and VA of the periodic table.

Other modifications and alterations of this invention will becomeapparent to those skilled in the art from the foregoing discussion,examples and accompanying drawing, and it should be understood that thisinvention is not to be unduly limited thereto.

What is claimed is:
 1. In an oxidative dehydrogenation processcomprising passing a feed stream comprising heated air, steam, andhydrocarbons into a dehydrogenation catalytic reactor, catalyticallyconverting the feed stream in the reactor, and discharging an effluentstream from the reactor for further processing, said reactor effluentcomprising water, dehydrogenated hydrocarbon, oxygenated hydrocarbonderivatives, and unconverted hydrocarbon, the improvement comprising:continuously during said process carrying out the steps of(A) separatingwater from the dehydrogenation reactor effluent; (B) passing theseparated water into a catalytic oxidation reactor; (C) treating saidseparated water in said catalytic oxidation reactor so as to convert anyorganic compounds therein to a carbonaceous gas; and thereafter (D)passing the treated water from said catalytic oxidation reactor into thedehydrogenation catalytic reactor.
 2. A process, as set forth in claim1, wherein the carbonaceous gas comprises carbon monoxide and carbondioxide.
 3. A process, as set forth in claim 1, wherein the hydrocarbonfeed stream to the dehydrogenation catalytic reactor comprises butenesand effluent from said reactor comprises butadiene.
 4. A process, as setforth in claim 1, wherein the treated water effluent of the catalyticoxidation reactor is steam.